Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M37/00—Other apparatus for introducing media into the body; Percutany, i.e. introducing medicines into the body by diffusion through the skin
  • A61M37/0015—Other apparatus for introducing media into the body; Percutany, i.e. introducing medicines into the body by diffusion through the skin by using microneedles
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M37/00—Other apparatus for introducing media into the body; Percutany, i.e. introducing medicines into the body by diffusion through the skin
  • A61M37/0015—Other apparatus for introducing media into the body; Percutany, i.e. introducing medicines into the body by diffusion through the skin by using microneedles
  • A61M2037/0053—Methods for producing microneedles

Definitions

• the subject matter described herein relates to generally to a process for manufacture of an array of microprojecfions for delivery of an active agent
• Microneedle arrays were initially proposed as a way of administering drugs through the skin in the 1970s, for example in expired U.S. Patent No. 3,964,482.
• Microneedle arrays can facilitate the passage of drugs through or into human skin and other biological membranes in circumstances where ordinary transdermal administration is inadequate.
• Microneedle arrays can also be used to sample fluids found in the vicinity of a biological membrane such as interstitial fluid, which is then tested for the presence of biomarkers.
• microneedle arrays in recent years it has become more feasible to manufacture microneedle arrays in a way that makes their widespread use financially feasible.
• U.S. Patent No. 6,451 ,240 discloses some methods of manufacturing microneedle arrays. If the arrays are sufficiently inexpensive they may be marketed as disposable devices, A disposable device may be preferable to a reusable one in order to avoid the question of the integrity of the device being compromised by previous use and to avoid the potential need of resteriiizing the device after each use and maintaining it in controlled storage.
• Much of the initial work in fabricating microneedle arrays has focused on silicon or metals as the material of choice. There are significant advantages to using a polymer aw the material for manufacture of a polymeric arrays.
• U.S. Patent No. 8,451 ,240 discloses some methods of manufacturing polymeric microneedle arrays. Arrays made primarily of biodegradable polymers have some advantages. U.S. Patent No. 6,945,952 and U.S. Published Patent Applications Nos. 2002/0082543, 2005/0197308 and 2008/0269685 describe microneedle arrays made of biodegradable polymers. A detailed description of the fabrication of a microneedle array made of poiyglycoiic acid is found in J ⁇ ng-Hwan Park et a!., "Biodegradable polymer microneedles: Fabrication, mechanics, and transdermal drug delivery," J. of Controlled Release, 104:51-68 (2005),
• a method of forming a microprojection array comprising a plurality of cavities that define individual microprojections in the array.
• a quantity of formulation is placed on a substrate, and the mold is placed in contact with the formulation so that the opening to each cavity in the plurality of cavities is in direct contact with the formulation.
• Ai! or a portion of the formulation is transferred into the plurality of cavities. Then, either the mold is disengaged from the formulation, or the formulation is withdrawn from contact with the mold, in such a way that the formulation transferred into the plurality of cavities is retained.
• a method of forming a microprojection array is provided.
• a moid is provided, the mold comprising a plurality of cavities for forming the microprojections.
• the mold is positioned in a fixture having first and second members, and at least one port.
• a formulation is introduced through the port into the fixture, for contact with openings to each of the cavities in the plurality of cavities in the mold.
• the formulation is transferred into the plurality of cavities, and then non-transferred formulation is withdrawn from contact with the mold at a rate whereby transferred formulation is retained in the plurality of cavities.
• the method in one embodiment, comprises dispensing a quantity of a formulation on a substrate, contacting a mold having a plurality of cavities for individual microprojections in the array with the formulation dispensed on the substrate, wherein the mold and the formulation are contacted such that the plurality of cavities are in fluid communication with the formulation, and then transferring formulation into the plurality of cavities.
• the mold is then disengaged from the formulation and the substrate in a manner that retains formulation in each of the plurality of cavities.
• transferring comprises transferring formulation into the plurality of cavities by applying pressure to the moid when in contact with the formulation dispensed on the substrate, In one embodiment, a pressure in the range of 0.1-1 atmosphere (10.1-101 kPa) is applied. In another embodiment, transferring comprises applying a vacuum to the mold when in contact with the formulation.
• the substrate has a reservoir or cavity.
• the substrate comprises channels for venting a gas.
• disengaging the mold from the formulation and the substrate achieves a uniform retention of formulation in each of the plurality of cavities, as evidenced by a standard deviation in amount of formulation retained in each cavity less than or equal to about 10% of the average amount of formulation retained in the cavities,
• disengaging the mold from the formulation and the substrate is achieved by lifting an edge of the mold and gradually peeling the mold from the formulation and substrate at a controlled rate.
• the controlled rate of disengaging is carried out by a rotatable member attachable to the mold.
• the method further comprises recovering formulation that is not retained in the plurality of cavities. In one embodiment at least about 90% of the formulation not retained in the plurality of the cavities is recovered.
• disengaging comprises disengaging at a rate of less than or equal to 5 mm/min.
• the method further comprises, in some embodiments, removing solvent from the formulation that is retained in the plurality of cavities. !n one embodiment, solvent is removed by placing the mold at a temperature to evaporate the solvent, in some embodiments, after removal of solvent, a second formulation is applied onto the mold.
• the mold in one embodiment, has a plurality of cavities that project into the mold from an approximately planar mold surface, [021] In another embodiment, for at least one cavity in the plurality of cavities, the diameter of the at least one cavity's intersection with a plane parallel Io the planar mold surface decreases monotonicaSly as a function of the plane's distance from the mold surface.
• the diameter of the intersection of the at least one cavity with a plane parallel to the planar mold surface decreases more rapidly as when the plane is close to the mold surface than when the plane is further from the mold surface.
• the diameter of the intersection of the at least one cavity with a plane parallel to the planar mold surface decreases linearly as a function of distance to the mold surface for a range of distances close to the mold surface and then decreases linearly but more slowly for a second range of distances further away from the mold surface.
• a method of fabricating a microprojection array comprises positioning a mold comprising a plurality of cavities for forming microprojections in an array of microprojections in a fixture, the fixture comprised of a first member and a second member and at least one port, the mold positioned between the first and second members.
• a formulation is introduced into the fixture through the at least one port such that the formulation contacts openings to the plurality of cavities in the mold. All or a portion of the introduced formulation is then transferred into the plurality of cavities; and then any non-transferred formulation is withdrawn from the fixture at a rate whereby formulation transferred into the plurality of cavities is retained in each cavity in the plurality.
• transferring comprises pressurizing the formulation within the fixture.
• the steps of transferring and withdrawing achieve a uniform retention of formulation in each of the plurality of cavities, as evidenced by a standard deviation in amount of formulation retained in each cavity less than or equal to about 10% of the average amount of formulation retained in the cavities.
• a microprocessor controls the steps of introducing and withdrawing formulation from the fixture.
• the mold positioned in the fixture is a mold wherein the plurality of cavities are elongated cavities with a longer dimension and a shorter dimension, and the mold is held in the fixture in a way that the longer dimension of each cavity in the plurality of cavities is approximately horizontal.
• the method in another embodiment, further comprises removing the mold with retained formuiation from the fixture.
• the method further comprises removing solvent from the retained formulation in each of the plurality of cavities to yield a dried formulation from which the microprojections it the array are composed.
• FIGS. 1 A-1 B depict schematically in side-view two different shapes of a single microprojection from an array, where in FIG, 1A, the diameter of the microprojection decreases more rapidly with distance from the base closer to the base compared to further away from the base.
• FIGS. 2A-2D depict schematically a method for filling a microprojection array mold with a formulation.
• FIGS. 3A-3B are computer-generated photomicrographs of a microprojection array after filling with a formulation (FiG. 3A) and after drying of the formulation (FIG. 3B).
• FIG. 4 is a computer-generated photomicrograph from an optical microscope, where the image is of microprojections in an array produced using the mold filling process described herein, wherein active agent that is concentrated in the tip of each microprojection is visible.
• FIG, 5 schematically depicts an arrangement for peeling a mold according to one of the methods described herein.
• FIGS. 6A-6B schematically depict a fixture for use in a method for filling microprojection cavities in a mold for a microneedle array with a liquid formulation that upon drying forms microprojections of the array.
• the mold in one embodiment, has a plurality of cavities that project into the mold from an approximately planar mold surface.
• the diameter of the at least one cavity's intersection with a plane parallel to the planar mold surface decreases monotonically as a function of the pian ⁇ 's distance from the mold surface.
• the diameter of the intersection of the at least one cavity with a plane parallel to the planar mold surface decreases more rapidly as when the plane is close to the mold surface than when the plane is further from the mold surface.
• the diameter of the intersection of the at least one cavity with a plane parallel to the planar mold surface decreases linearly as a function of distance to the mold surface for a range of distances close to the mold surface and then decreases linearly but more slowly for a second range of distances further away from the mold surface.
• skin as the biological membrane through which the active is administered. It will be understood by persons of skill in the art that in most or all instances the same inventive principles apply to administration through other biological membranes such as those which line the interior of the mouth, gastro-infestina! tract, blood-brain barrier, or other body tissues or organs or biological membranes which are exposed or accessible during surgery or during procedures such as laparoscopy or endoscopy.
• microneedles as a type of microprotrusion or microprojection which is being employed. It will be understood by persons of skill in the art that in many cases the same inventive principles apply to the use of other microprotrusio ⁇ s or microprojections to penetrate skin or other biological membranes.
• Other rnicroprotrusions or microprojections may include, for example, microblades as described in U.S. Patent No. 6,219,574 and Canadian patent application no. 2,228.718, and edged microneedles as described in U.S. Patent No. 6,652,478.
• the microprojections have a height of least about 50 ⁇ m, of at least about 100 ⁇ m, at least about 150 ⁇ m, at least about 200 ⁇ m. at least about 250 ⁇ m, or at least about 300 ⁇ m. In general it is also preferred that the microprojections have a height of no more than about 1 mm. no more than about 500 ⁇ m, no more than about 300 ⁇ m, or in some cases no more than about 200 ⁇ m or 150 ⁇ rn.
• the microprojections may have an aspect ratio of at least 3:1 (height to diameter at base), at least about 2:1 , or at least about 1 :1.
• a shape for the microprojections is a cone with a polygonal base, for example hexagonal or rhombus- shaped.
• Other possible microprojection shapes are shown, for example, in U.S. Published Patent App. 2004/0087992.
• Microprojections may in some cases have a shape which becomes thicker towards the base, for example microprojections which have roughly the appearance of a funnel, or more generally where the diameter of the microprojection grows faster than linearly with increasing distance to the microprojection's distal end. Such a shape is beneficial to, for example, facilitate demolding.
• FIG. 1A schematically depicts in side- view an individual microprojection 10 of this type. As may be seen in the figure, the diameter D of the microprojection's intersection with a plane parallel to a base 12 decreases as the plane moves away from base 12 and closer to a tip 14 of the microprojection. In addition, this diameter decreases more rapidly close to base 12, in basement zone 18, than it does further away from the base, in tip zone 18.
• microprojections are thicker towards the base, a portion of the microprojection adjacent to the base, which is referred to herein as a 'basement" region or a "foundation" region, approximately identified by zone 16 in FIG. 1A is designed not to penetrate the skin by virtue of its increasing diameter.
• a 'basement region or a "foundation” region approximately identified by zone 16 in FIG. 1A is designed not to penetrate the skin by virtue of its increasing diameter.
• the microprojection of FIG. 1A is merely exemplary, and another example of a single microprojection In an array is illustrated in FIG. 1 B.
• the number of microprojections in an array is preferably at least about 100, at least about 500» at least about 1000, at least about 1400, at least about 1600, or at least about 2000.
• the area density of microprojections may not be particularly high, but for example the number of microprojections per cm 2 may be at least about 50, at least about 250, at least about 500, at least about 750, at least about 1000, or at least about 1500.
• a method of forming a rnicroprojection array such as those described above, is provided.
• a rnicroprojection array mold 20 is provided, the mold comprising a plurality of cavities that define individual microprotrusions or microprojections in the array.
• the microprojections are not visible in FIGS. 2A-2D due to their small size.
• Each cavity in the plurality of cavities has an opening and internal surface with dimensions, e.g, diameter and height, selected to provide a desired microprojection configuration.
• the internal dimensions of the cavities have a certain height (or length) and diameter, which can vary along the height as evident from the exemplary microprojections shown in FIG. 1A-1 B.
• the dimensions of the microprojection cavities in the mold correlate exactly or approximately, depending on various factors in the manufacturing process, to the dimensions of the finished microprojections in the array. A skilled artisan will appreciate that ihe cavities in the mold can all be the same or can differ, to yield a microprojection array with the same or differing microprojections.
• An optional release layer such as a silicon sheet, can be placed on an upper surface 26 of the substrate to facilitate removal of the mold from the substrate.
• the substrate can include a recess or depression to retain the formulation (not shown in FIG. 2A).
• substrate may also optionally comprises channels for venting a gas.
• the mold is placed in direct contact with formulation 22, wherein the mold is oriented such that the opening to each cavity is in contact with the formulation. With respect to the drawing in FIG. 2A, the opening to each cavity is facing down. That is, the mold has an upper surface 28 whereupon the openings to each cavity in the plurality of cavities that define each microprojection in the array are disposed, and the upper surface is placed directly in contact with the formulation, such that the formulation can fill each cavity.
• the formulation is moved or transferred info the cavities by a suitable means.
• the suitable means is pressure, indicated in FIG. 2C by arrows, such as arrow 30.
• the mold, formulation, and substrate are placed, for example, in a pressure chamber, in order to transfer formulation into each cavity.
• a mold designed with a port on the surface opposing upper surface 28 or on a side wall can provide for attachment of a vacuum to achieve movement of the formulation into the plurality of cavities.
• the mold is peeled away from the precursor formulation and the substrate in such a way that precursor is retained in the mold cavities, as depicted in FIG. 2D.
• the mold may be manufactured by a wide variety of available techniques discussed in the literature. For example, it may be made by techniques discussed in U.S. Published Patent Application No. 2008/0289685.
• the mold may be made of synthetic polymeric materials having suitable mechanical properties.
• the mold should have mechanical properties such that the peeling step of the method can be carried out without difficulty and without damage to the mold.
• the mold is fabricated from a flexible, polymeric material and in one embodiment is hydrophobic, and in another embodiment is permeable to oxygen, nitrogen and/or carbon dioxide.
• the substrate may be flat on the side facing the mold. Alternatively, and as mentioned above, it may have a depression or cavity suitable for holding the microprojection precursor formulation.
• the substrate may be made, for example, of the same material of which the mold itself is made.
• the substrate may also be made of a polymer resin, such as polytetrafluoroethylene, polyethylene or polypropylene, or a metal, such as stainless steel, titanium or gold.
• a material is placed in the depression which retains the formulation, particularly in the case where the mold and the substrate are hydrophobic in nature.
• a materia! placed in the cavity assists with distribution of the formulation in the depression and wetting of the interface between the substrate and the mold.
• An exemplary material is a non-woven material or non-woven netting fabric, such as a non-woven polyolefin available under the tradename DELNET 6' (Delstar Technologies, Inc.. Middletown, DE).
• the placement of the precursor formulation may be done by dispensing, for example with a pipette, a single drop of precursor formulation on the substrate. Alternatively, more than one drop may be dispensed on the substrate, where the multiple drops can be arranged in a desirable pattern. If there is a depression in the substrate, the drop or drops may be placed in that depression.
• the step of applying pressure to the mold, formulation, and substrate may be carried out, for example, by placing the components in a pressure chamber. Pressures greater than 0.2 atmospheres or greater than 0.5 atmospheres or greater than 1 atmosphere above atmospheric pressure may be employed. [055] A purpose of the step of applying pressure is to replace the air in the mold cavities with precursor formulation. There are other available techniques which help to achieve this objective, such as those set out in Published Patent Application No. 2008/0289885. It may be desirable to employ one or more of these alternative techniques and not carry out the step of applying pressure.
• Example 3 below provides details on manufacture of microprojection arrays according to the processes described in FSGS. 2A-2D.
• a metal substrate with a silicone release sheet was provided.
• a polymer and fluorescin formuSation was applied to the silicone sheet, and the mold of the microprojection array was piaced on the formulation, with the openings to each cavity in the mold in direct contact with the formulation.
• the substrate-silicone sheet-formu!atlon ⁇ mo!d assembly was placed in a pressure chamber to transfer the formulation into the cavities of the mold. After removal of the pressure, the mold was removed from the assembly by lifting one edge of the mold and lifting so that the mold gradually disengages from the assembly.
• FIGS. 3A-3B The microarrays prepared according to Example 3 were inspected optically, and the results are shown in FIGS. 3A-3B.
• FIG. 3A a photomicrograph of the upper surface of the microprojection array is seen, where the wet formulation is visible by virtue of the fiuorescin dye. After the process of filling the microprojection cavities in the moid, the formulation is substantially or completely disposed within the cavities and essentially no formulation is on the surface of the moid between cavity openings.
• FIG. 3B shows the microarray after drying of the formulation and loss of solvent from the formulation, with the fSuorescin dye, representative of an active drug, is deposited In the tip region of each microprojection.
• FIG, 4 is an artists rendering of an optical photomicrograph of microprojectio ⁇ s in the array, the array fabricated from the process detailed in FIGS. 2A- 2D.
• active agent is disposed primarily in the tip of each microprojection, and the larger diameter basement region of each microprojection (basement zone 16 in FiG. 1A) is essentially free of active agent.
• a skllSed artisan will appreciate that the orientation of the components in the process can be reversed, and the component that is removed, or 'peeled' away, changed.
• a quantity of formulation can be placed on a mold which has the cavities facing up.
• a flexible substrate or sheet of material is placed atop the formulation. Pressure is applied to the sheet, precursor formulation, and mold. The substrate is peeled away or disengaged from the formulation and the mold in such a way that formulation is retained in the mold cavities.
• the peeling step may be accomplished, for example, manually with the fingers or more typically with an implement, such as tweezers, in carrying out the peeling manually, it may be desirable to watch the microprojection precursor formulation that is between the mold and the substrate and see that it is receding smoothly as the peeling operation ensues. It may also be desirable to attempt to maintain a more or less constant rate of peeling. The rate may be measured, for example, in millimeters per minute. Rates between about 1-10 mm/minute, about 3-7 mm/minute, or about 4-6 mm/minute may be employed.
• the peel rate be controlled so that only microprojection formulation is left in the cavities of the mold.
• none of the formulation should form a bridge between cavities or form droplets on the surface of the mold outside the cavities.
• a mechanism may be employed to peel the moid away from the arrangement of components.
• the mechanism may be a cylinder which is rolled over the substrate at a controllable speed, with the mold attached to the cylinder with the mold cavities facing outward.
• the mold may be attached, for example, with an adhesive.
• the attachment may take place by using a mechanical mode of attachment, for example protrusions that fit through holes in the moid or a mechanism that clips onto an end of the moid.
• FIG. 5 depicts schematically a mechanism for peeling a mold 30 from a substrate 32 which has a shallow reservoir 34 in which a microprojection precursor formulation is retained. After dispensing a formulation into the reservoir, a microneedle mold is placed over the formulation-filled reservoir, so that the openings to each cavity in the mold is accessible by the formulation. Ail or a portion of the formulation is transferred into the cavities of the mold, for example, by placing the substrate, formulation and mold in a pressure vessel. Then, and with specific reference to FIG.
• the substrate, formulation, and mold are brought in contact with a cylinder 38
• the cylinder is rotatable by a mechanism 38 which may be based, for example, on a screw drive or on a stepper motor driving a pulley (not shown) or on any other manner of producing a linear motion of the cylinder parallel to the substrate, leaving the cylinder free to rotate.
• a mechanism 38 which may be based, for example, on a screw drive or on a stepper motor driving a pulley (not shown) or on any other manner of producing a linear motion of the cylinder parallel to the substrate, leaving the cylinder free to rotate.
• the mold detaches from substrate 32.
• suitable speeds and with suitable mold cavities and formulation material properties e.g., viscosity, surface tension
• cavities in the mold that define each microprojection in the array retain formulation thai, upon removal of the solvent from the form ⁇ iation, yields a solid material in each cavity that is a microprojection.
• pressure is merely exemplary.
• Another approach is to apply a vacuum to the cylinder so that as the mold detaches from the substrate, formulation fluid is drawn into each cavity, [062]
• the mechanism 38 may operate under the control of an electric motor, which in turn may operate under the control of a computer or microprocessor.
• the use of electric motors to produce controlled motion over a short range is well known in the art, as is the computer control of electric motors.
• the rate of peeling will have an influence on whether microprojection precursor formulation is retained in the mold cavities.
• a higher rate of peeling i.e, a faster rate of removal of the moid from the formulation, tends to leave residual formulation droplets on the surface of the mold, whereas a lower rate of removal may pull all precursor formulation out of the cavities in the moid.
• removal of the mold from contact with the formulation is selected to achieve the fastest removal rate with optimal and reliable retention of formulation in the mold cavities.
• Retention of formulation in the cavities of a moid may be determined, for example, by examining the cavities under a microscope to see if they appear partially filled, as depicted in FIG. 3B.
• Example 4 describes another example of manufacture of a rnicroprojection array according to the processes described In FiGS. 2A-2D.
• a microprojection array fabricated from a precursor formulation of dextran, sorbitol, the active agent human parathyroid hormone, in histidine buffer.
• a moving member such as a cylinder as depicted in FlG. 5.
• the cylinder was rotated to disengage the mold from the reservoir, where the step of disengaging the moid from the substrate was performed under conditions such that formulation transferred into the cavities of the moid was retained in the cavities, and the amount of formulation across the plurality of cavities was substantially uniform, in this example, the uniformity of formulation retained in the cavities of the moid was measured by quantifying the amount of active agent (human parathyroid hormone) in each rnicroprojection.
• the coefficient of variation in the amount of active agent across the array of microprojections was 10%. In other embodiments, a coefficient of variation of iess than 10%, more preferably of less than 7%, and still more preferably of less than about 5% or 3% is preferred.
• microprojections may in some cases have a shape which becomes thicker towards the base, for example microprojections which have roughiy the appearance of a funnel, or more generally where the diameter of the rnicropr ⁇ jection grows faster than linearly with increasing distance to the microprojection's distal end.
• This shape of microprojection is depicted in FIG. 1 A, where the basement region 16 is also referred to herein as a "funnel" due to its funnel-like shape.
• the thinner (distal) end of the funnel may retain microprojection precursor while the thicker (proximal) end of the funnel does not retain it,
• the amount of microprojection precursor formulation retained in the cavities be approximately the same from one cavity to the next.
• the standard deviation of the volume of precursor formulation be less than about 30%, less than about 20%, iess than about 10%, iess than about 5%, or less than about 2% of the average volume of precursor formulation in the cavities which retain precursor formulation.
• An alternative manner of measuring the variation in the amount of precursor formulation from one cavity to the next in an array is in terms of the amount of active agent for the embodiments where the microprojection precursor formulation contains an active agent.
• the standard deviation of the volumes or weights of active agent in the plurality of cavities in the microprojection array mold be less than about 30%, less than about 20%, less than about 10%, less than about 5%, or less than about 2% of the average volume or weight of active agent in the cavities which retain precursor formulation.
• another method of forming a microprojection array is provided.
• one or more molds for a microneedle or microprojection array is secured in a fixture formed of two member, or halves, that mate in such a way to form a reservoir in which the one or more molds is disposed.
• a port is provided through the fixture and into the reservoir, through which a formulation material for formation of the microprojections in the array can be introduced.
• a second port or vent allows for passage of air that is displaced upon introduction of the formulation.
• the reservoir is filled with formulation in an amount sufficient to fill the plurality of cavities in the mold.
• the fixture is then exposed to a means that transfers the formulation from the reservoir into the pluralities in the mold, the means including pressure or vacuum or a combination of pressure and vacuum, Any formulation that is not transferred into the cavities in the moid is then controllably removed so that formulation transferred to the cavities is retained in the cavities, yet excess formulation is withdrawn. Desirably none of the formulation forms a bridge between cavities or forms droplets on the surface of the mold outside the cavities.
• FIGS. 8A-8B An exemplary apparatus suitable for practicing this embodiment is shown schematically in FIGS. 8A-8B.
• a mold 42 is held between first and second members, 44, 48, of the fixture.
• First member 44 has an inner surface 48
• second member 46 has an inner surface 50.
• One of the members, in this embodiment the second member has a cavity 52 defined by a recessed floor 54 and sidewalls 56, 58.
• First and second ports, 60, 62 provide fluid communication between the external environment and cavity 52.
• ports 80, 62 are used during the process for venting and pressurization with a gas, for introduction of formulation, and/or for evacuation of cavity (e.g., vacuum evacuation or pressurized evacuation).
• FlG. 8B is a cross-sectional top view of second member 48 taken along line B-B in FIG. 6A, that shows cavity 52 and ports 60, 62. [070] in use.
• one or more microprojection molds which has openings to a plurality of cavities that define individual microprojections in the array is placed in the reservoir formed when the first and second members of the fixture are brought into contact. In FIG.
• a single mold 42 is secured adjacent cavity 52, where the openings to the plurality of cavities defining the microprojections of the array are in fluid communication with the cavity 52, also referred to as a reservoir when the two members are in a mating arrangement,
• the reservoir has a depth of at ieasf 0.05 mil (0.00127 mm), more preferably of at least 0,1 mi! (0.00254 mm).
• the microprojection openings and the cavities are not shown in FIG, 8A due to their small size.
• Formulation is introduced through one of the ports, such as port 62, and air or gas in the cavity is vented through the other port, such as port 60.
• Enough formulation is introduced into the cavity to cover the plurality of openings to the cavities in the mold.
• One of the ports is then closed, for example by suitable vaiving, and the reservoir is pressurized to a desired.
• a pressure gauge can be attached in member 46 to measure pressure in the cavity 52. Pressurization of the reservoir can be achieved by introducing additional formulation into the reservoir after closing one of the ports or, alternatively, a pressurized gas may be introduced through one of the ports until the desired pressure in the reservoir is reached.
• the mold cavities desirably will remain covered with the formulation while the reservoir is being pressurized.
• the fixture may be provided with a mechanism which allows members 44, 46 to be separated and brought together using a handle or other convenient means of manipulation.
• the mechanism may be designed so that in a closed position the two members are pressed together, it may be desirable to place the microprojection array mold into the member with the cavity when the member is in a horizontal position, and then have the member which holds the mold movable into a vertical position for mating with the opposing member to form the fixture with the mold secured there between.
• the fixture is designed to contain more than one microprojection array mold, where the molds can be side-by-side with the openings to the cavities facing the reservoir or where the molds are situated in an opposing arrangement, so that the openings to the cavities face each other.
• a "uniform" volume of formulation intends a standard deviation of the volumes or weights of active agent in the plurality of cavities in the microprojection array mold be less than about 30%, less than about 20%, less than about 10%, less than about 5%, or less than about 2% of the average volume of formulation or weight of active agent in the cavities which retain precursor formulation.
• One variable which may affect under some circumstances whether microprojection precursor formulation remains in the cavities is the rate at which the formulation is removed from the reservoir, after the step of transferring the formulation into the cavities, for example by pressurization of the reservoir in the fixture.
• a controlled rate of withdrawal of formulation that remains in the reservoir after transfer of formulation into the plurality of cavities is selected, so that formulation that did not transfer into a cavity and remains in the reservoir is removed while retaining within each cavity the entire amount of formulation that was transferred into the microprojection cavity that will form the tip zone of each microprojection.
• a withdrawal rate of between about 0.1 cm/min and about 10 cm/min, or between about 0.2 crn/min and 2 cm/min, or between about 0.5 cm/min and 1 ,5 cm/min is generally suitable. The fill rate can be faster compared to the withdrawal rate.
• the withdrawal rate in cm/min might not be proportional to the withdrawal rate in mL/min.
• the withdrawal rate in mL/min may be varied, for example, by starting slowly (at the top of the reservoir), increasing until the level reaches the middle of the reservoir, and decreasing until the bottom of the reservoir is reached.
• a fixture dimensioned for retention of a single microprojection array moid in the fixture reservoir was used (referred to in Exampie 6 as a 'one-up' reservoir), and a fixture dimensioned for retention of two microprojection array molds in the fixture reservoir used (referred to in Example 6 as a 'two-up' reservoir).
• formulation was introduced into the reservoir via one of the ports, with the second port in an open position to ⁇ ent air in the reservoir. Then, the second port is ciosed and the pressure in the reservoir is Increased to transfer the formulation into the piur ⁇ lirty of cavities in the mold(s).
• the solvent in the formulation in the mold cavities was removed, by for example, placing the fixture containing the molds in an oven.
• the process was then repeated with a second formulation introduced into the reservoir of the fixture, to form a microprojection array wherein the basement region of each microprojection had a composition differing from the composition of the tip region.
• a moid with roughly funnel-shaped cavities can be used.
• the moid may be manufactured by a wide variety of available techniques discussed in the literature. For example, it may be made by techniques discussed in U.S. Published Patent Application No, 2008/0269885.
• the mold may be made of synthetic polymeric materials having suitable mechanicai properties, in general, molds may be used in this embodiment which are less flexible than those used in the peeling embodiment.
• removal of formulation from the fixture and/or introducing formulation into the fixture can be accomplished by any number of techniques, including but not limited to, manually or under the control of a microprocessor to ensure a uniform rate of fluid movement, In the working examples, a microprocessor-controiied syringe pump was used to introduce fluid into the fixture, and to remove fluid there from.
• the mold cavities may be dried to remove solvent from the formulation, to yield a solid material in each cavity that forms the microprojections in the array.
• One or more additional layers of formulation may be applied over the first, preferably after it has dried, by the same or different method. Examples 1 and 2 together illustrate this approach, As a skilled artisan will appreciate, the additional formuiation can have a different composition from the first, where the first formulation typically contains the active agent so that the agent is disposed in the tip of the microprojections, and the second formulation lacks active agent and forms the basement region of the microprojections that may not penetrate the stratum corneum.
• the various steps in the methods described herein, involving dispensing formulation, contacting formulation with the mold, transferring formulation into cavities of the mold, and disengaging the mold from the formulation or withdrawing formulation from a fixture, individually or collectively, can be conducted at a the same or different temperatures. In one embodiment all of the steps are conducted at room temperature, e.g., of between about 23-25 0 C. recovering formulation that is not retained in the plurality of cavities.
• the methods described herein can include the step of recovering formulation that is not retained in the plurality of cavities in the mold. For example, after withdrawing formulation from the fixture, the formulation can be recovered for reuse or for analysis. For example, after disengaging the mold from the formulation deposited on the substrate, the formulation can be recovered for reuse or analysis. In one embodiment, at least about 90%, preferably 95%, of the formulation not retained in the plurality of the cavities is recovered.
• transfer of formulation into the plurality of cavities is achieved by a transfer step, which can be, for example, pressurizing the formulation, intending the formulation that is introduced into the reservoir of the fixture or the formulation that is deposited on a substrate (in which case the substrate-formulation and moid are generally pressurized together).
• a transfer step can be, for example, pressurizing the formulation, intending the formulation that is introduced into the reservoir of the fixture or the formulation that is deposited on a substrate (in which case the substrate-formulation and moid are generally pressurized together).
• a transfer step can be, for example, pressurizing the formulation, intending the formulation that is introduced into the reservoir of the fixture or the formulation that is deposited on a substrate (in which case the substrate-formulation and moid are generally pressurized together).
• a skill artisan can select a pressure that is suitable to achieve transfer of the formulation into the cavities of the mold, and will appreciate the variables that guide selection of the optimal pressure, including but not limited to volume, properties of the formulation, area, and temperature.
• a pressure in the range of 0.1 -1 atmosphere (10.1 -101 kPa) is selected, and in preferred embodiments, a pressure of at least about 0.1 atm(10.1 kPa), at least about 0.5 atm (50.7 kPa), or at least about 1.0 atm (101 kPa) Is applied.
• formulations for the Microprojections and the Microprojection Array [084]
• the formulation is referred to also as a "precursor formulation" to reflect that the formulation introduced into the mold cavities is a precursor of the resulting solid material from which the microprojections and/or microprojection array are made.
• the solvent of the precursor formulation is removed to yield the final material from which the microarray is made, however other changes to the
• precursor formulation can be designed to occur (such as cr ⁇ ss ⁇ nking or reactions) or occur by happenstance,
• the precursor formulations comprise at least one active agent (e.g. drug or therapeutic agent), at least one solvent, an optional polymer, and other optional ingredients such as sugars, antioxidants, preservatives, etc.
• the precursor formulations comprise at least one polymer, at least one solvent, an optio ⁇ ai active agent, and other optional ingredients such as sugars, antioxidants, preservatives, etc.
• surfactants would be added to adjust surface tension.
• the active therapeutic agents which may be placed in microprojections by the methods described herein include, but are not limited to, small molecule drugs, proteins, peptides, nucleic acids, and the like.
• human parathyroid hormone hPTH
• Vaccines are another exemplary therapeutic agent that can be included in the formulation for disperment in the microprojections of the array.
• U.S. Published Patent Application No. 2008/0289885 discloses a wide variety of suitable actives, all of which are incorporated by reference herein.
• the microprojection precursor formulation may comprise one or more polymers.
• the polymers are preferably biocompatible.
• the polymers are preferably biodegradable.
• a polymer will degrade under expected conditions of in vivo use (e.g., insertion info skin), irrespective of the mechanism of biodegradation.
• Exemplary mechanisms of biodegradation include disintegration, dispersion, dissolution, erosion, hydrolysis, and enzymatic degradation.
• Exemplary polymers suitable for use in microprojection precursor formulations include, bui are not limited to, po!y(lactic acid), poly(glycolic acid), poly(iactic acid-co- glycolic acid), poly(caprolactone), polyanhydrides, polyamines, polyesteramides, polyorthoesters, polydioxanones, polyacetals, polyketals, polycarbonates, polyphosphoesters, polyorthocarbonates, poSyphosphazenes, poiy(rnalic acid), poly(amino acids), hydroxycellulose, poiyphosphoesfers, dextran, tetrastarch, natural or modified polysaccharides, hyalouronidase, chitin.
• the formulation comprises dextran, and is preferably a dextran with a molecular weight of between about 20.000-100,000 Daltons, more preferably of between 40,000-80,000 Daltons, and still more preferably of between 40,000-70,000 Daltons. In specific examples, dextran with a molecular with of 70,000 Daltons (70 kDa) is used.
• the microprojection precursor formulation may also comprise one or more sugars.
• Exemplary sugars which may be included in a microprojection array include dextrose, fructose, galactose, maltose, maltulose, iso ⁇ ma!luiose, man ⁇ ose, lactose, lactulose, sucrose, and trehalose.
• Sugar alcohols for example iactitol, maltitol, sorbitol, and mannitoi, may also be employed.
• Cyclodextrins can also be used advantageously in microprojection arrays, for example ⁇ , ⁇ , and y cyclodextrins, for example hydroxypropyi- ⁇ -cyclodextrin and rnethyl- ⁇ -cyclodextrin.
• sorbitol is a sugar included in the formulation, and in another embodiment, the formulation comprises sorbitol and a dextran.
• biodegradability of a microprojecfion array may be facilitated by inclusion of water-swe ⁇ able polymers such as cross ⁇ nked PVP, sodium starch glycolate, celluloses, natural and synthetic gums, or alginates.
• water-swe ⁇ able polymers such as cross ⁇ nked PVP, sodium starch glycolate, celluloses, natural and synthetic gums, or alginates.
• Suitable active agents include the broad classes of compounds such as, by way of illustration and not limitation: analeptic agents; analgesic agents; antiarthritic agents; anticancer agents, including antineoplastic drugs; anticholinergics; anticonvulsants: antidepressants; antidiabetic agents; antidiarrheais: antihelminthics: antihistamines; antihyperlipidemic agents; antihypertensive agents; anti-infective agents such as antibiotics, antifungal agents, antiviral agents and bacteriostatic and bactericidal compounds; antiinflammatory agents; antimigraine preparations; antinauseants; antiparkinsonism drugs; antipruritics; antipsychotics; antipyretics; antispasmodics; antitubercular agents; antiulcer agents; anxiolytics; appetite suppressants; attention deficit disorder and attention deficit hyperactivity disorder drugs; cardiovascular preparations including calcium
• peptides and proteins which may be used with micro-projection arrays are oxytocin, vasopressin, adrenocorticotropic hormone (ACTH), epidermal growth factor (EGF), prolactin, luteinizing hormone, follicle stimulating hormone, luliberin or luteinizing hormone releasing hormone (LHRH), insulin, somatostatin, glucagon, interferon, gastrin, tetragastrin, pentagastrin, urogastrone, secretin, calcitonin, enkephalins, endorphins, kyotorphin, taftsin, thymopoietin, thymosin, thymostimulin, thymic humoral factor, serum thymic factor, tumor necrosis factor, colony stimulating factors, motilin, bombesin, dinorphin, neurotensin, cerulein, bradykinin, urokin
• iysozyme chloride renin, bradykinin, tyrocidin, gramicidines, growth hormones, melanocyte stimulating hormone, thyroid hormone releasing hormone, thyroid stimulating hormone, parathyroid hormone, pancreozymin, cholecystokinin, human placental lactogen, human chorionic gonadotropin, protein synthesis stimulating peptide, gastric inhibitory peptide, vasoactive intestinal peptide, platelet derived growth factor, growth hormone releasing factor, bone morphogenic protein, and synthetic analogues and modifications and pharmacologically active fragments thereof.
• Peptidyl drugs also include synthetic analogs of LHRH, e.g., buserelin, deslorelin, fertirelin, gosereiin, histrelin, leuprolide (leuproreiin), lutreiin, nafarelin, tryptorelin, and pharmacologically active salts thereof.
• Macromolecuiar active agents suitable for microprojection array administration may also include biomolecules such as antibodies, DNA, RNA, antisense oligonucleotides, ribosomes and enzyme cofactors such as biotin, oligonucleotides, plasmids, and polysaccharides.
• Oligonucleotides include DNA and RNA, other naturally occurring oligonucleotides, unnatural oligonucleotides, and any combinations and/or fragments thereof.
• Therapeutic antibodies include Orthocione OKT3 ⁇ muromonab CD3), ReoPro (abciximab), Rituxan (rituxirnab), Zenapax (daclizumab), Remicade (infliximab), Simulect (basiliximab), Synagis (palivizumab), Herceptin (trastuzumab).
• Mylotarg gemtuzumab ozogamicin
• CroFab DigiFab
• Campath alemfuzumab
• Zevaiin ibritumomab tiuxetan
• Macromolecuiar active agents suitable for microprojection array administration may also include vaccines such as, for example, those approved in the United States for use against anthrax, diphtheria/tetanus/pertussis, hepatitis A, hepatitis B, Haemophilus influenzae type b, human papillomavirus, influenza, Japanese encephalitis, measles/mumps/rubella, meningococcal diseases (e.g., meningococcal polysaccharide vaccine and meningococcal conjugate vaccine), pneumococcal diseases (e.g., pneumococcal polysaccharide vaccine and meningococcal conjugate vaccine), polio, rabies, rotavirus, shingles, smallpox, tetanus/diphtheria, tetanus/diphtheria/pertussis, typhoid, varicella, and yellow fever.
• vaccines such as, for
• microprojection arrays penetrate human skin, it may be desirable to take steps which tend to eliminate the presence of microorganisms in the array. Such steps include, for example, the use of a formulation with high sugar concentration which will act as an osmotic agent to dehydrate microorganisms in the formulation.
• An alternative technique is the use of a non-physiologica! pH (e.g., below pH 6 and above pH 8) to retard growth and destroy microbial viability.
• the formulation may be made with organic solvents which are then dried in order to dehydrate microorganisms. Apart from the dehydration effect, the use of organic solvents is also inherently bactericidal since they disrupt bacterial cell membranes.
• the microprojection arrays may be packaged in a sealed, low oxygen environment to retard aerobic microorganisms and eventually destroy their viability.
• the arrays may also be packaged in a low moisture environment to dehydrate microorganisms.
• a further technique to deal with microorganisms is to include a pharmaceutically acceptable antimicrobial agent in the formulation or the packaging.
• a pharmaceutically acceptable antimicrobial agent examples include benzalkonium chloride, benzyl alcohol, chiorbutanoi, meta cresol, esters of hydroxyl benzoic acid, phenol, and thimerosal.
• a surfactant or detergent can be added to the formulation to disrupt the cell membrane of any microorganisms to kill them.
• a desiccant could be added to the packaging to dehydrate microorganisms and kill them.
• Antioxidants may be added to the formulation, for example to protect the active from oxidation.
• antioxidants include methionine, cysteine, D-al ⁇ ha tocopherol acetate, DL-alpha tocopherol, ascorbyl palmifafe, ascorbic acid, butylated hydroxyanisole, butyiated hydroxyquinone, butylhydroxyanisole, hydroxycornarin, butylated hydroxytoluene, cephalin, ethyl galiate, propyl gallate, octyl gailate, lauryl gallate, pr ⁇ pylhydroxybenzoate, trihydroxybutyrophenone, dimethylphenol, ditertbutylphenol, vitamin E, lecithin, and ethanolamine.
• a microneedle mold is sterilized by e.g. dry heat or gamma irradiation.
• An amount of the formulation (referred to herein as a precursor formulation), for example, 20 ⁇ L, is dispensed on the mold.
• the formulation is spread manually over the mold using a transfer pipette with a trimmed tip.
• the mold covered with formulation is then vortexed for five seconds using a commercial vibrating instrument to uniformly distribute the formulation across the moid.
• the mold with the formulation covering it is placed in a pressure vessel under 1 aim for about 10 minutes. Pressure is then removed. The mold is placed in an incubator at a temperature of 32 0 C, for about 30 minutes to 1 hour. The array is then demolded using double-sided adhesive tape, and is optionally attached to a backing.
• an additional layer is cast on the mold using a similar procedure.
• the additional layer consists of 75 ⁇ L of 20 wt% of the methacrylate cationic copolymer EUDRAGIT ® EPO (cationic copolymer based on dirnethylaminoethyl methacrylate, butyl methacrylate, and methyl methacryiate ) in a 3:1 mixture of ethano! and isopropy! alcohol.
• the additiona! layer is applied uniformly to the mold using a glass slide.
• the mo!d is placed in a pressure vessel and pressurized at 1 aim for 2 minutes. The pressure is released and the moid is allowed to dry in the pressure vessel for an additional five minutes, without disturbing.
• the mold is again dried in the incubator for 1 hour at 32°C, and then demolded.
• a microprojection array was manufactured as follows. A silicone sheet was placed on a fiat metal substrate. 125 ⁇ L of a microprojection precursor formulation was dispensed as a drop on the silicone sheet using a micropipette. A flexible, polymeric microprojection array moid made of silicone was placed on the formulation with the plurality of openings to the plurality of cavities that define individual microprojections facing the formulation and the top surface of the mold in direct contact with the formulation. Each cavity in the plurality of cavities, wherein the cavity included both the tip region and the basement (or "funnel” region) had a volume of about 1 nl_.
• the formulation was spread to cover a 1" x 1" (2.54 cm x 2.54 cm) area in the mold by manually applying pressure to the back side of the mold with tweezers.
• the assembly was placed in a pressure vessel and pressurized at 50 psi (344.7 kPa) for 1 minute. Pressure was released and the assembly was removed from the pressure vessel. Gripping one corner of the moid with tweezers, the mold was peeled from the silicone sheet.
• the silicone mold with formulation in the cavities was dried in an incubator at 32 0 C for 30 minutes to 1 hour. As shown in FIG. 3B, the cavities continue to appear uniformly filled after drying. The mold was then placed on the mold carrier, alignment with a TEFLON ® wiper was checked, and the wiper clearance was set at 17 mils (0.043 cm) from the lowest point on the moid. 700 ⁇ L of a second formulation, a "basement" solution, was loaded in the array area and spread with a polyefhyeiene terephthaiate (PET) cover slip. The mold with basement solution was pressurized at 50 psi (344.7 kPa) for 1 minute.
• PET polyefhyeiene terephthaiate
• a forrnuiation comprised of 14% dextra ⁇ 70, 4.8% sorbitol, 2.8% human parathyroid hormone (1 - 34) (hPTH) in histidine buffer solvent, pH 5,5, was prepared.
• the formulation was sterile filtered through a 0.22 micron filter. 250 ⁇ !_ of the formulation was dispensed into a shallow reservoir, a pre-ster ⁇ ized silicone mold was placed on atop of shallow reservoir with the openings to each cavity of each microneedle in the mold downward facing so that the formulation can enter the cavities.
• microprojection cavities in the mold were filled with the precursor formulation by pressurization of the substrate with the formulation-filled reservoir and the mold to 50 psi (344.7 kPa) in a pressure chamber for 1 minute.
• the mold was then attached to a cylinder and the cylinder was rotated with a speed of 2 - 4 mm/min to peel the moid from the shallow reservoir.
• the desirable amount of precursor formulation was retained in the cavities of the mold and dried at 32 0 C for 30 minutes.
• a basement layer was coated on atop of dried precursor as described in Example 3, to form a microstructure array (die cut into 1 cm 2 in diameter), To analyze the hPTH content in each microprojection array, the array was optically inspected, and a photomicrograph is shown in FIG. 4.
• the microarray was dissolved in buffer and hPTH content was measured by HPLC. With a sample size of 30 arrays tested, the average hPTH content per array was 32,9 ⁇ g with the coefficient of variation of 10%.
• a 1 inch by 1 inch (2.54 cm x 2.54 cm) mold for a microprojection array was provided.
• a microprojection precursor formulation comprised of 2.1 % hPTH (1-34). 14% fetrastarch, 4.8% sorbitol in histidine buffer solvent. pH 5.5 was prepared.
• a fixture comprised of first and second members was provided (FIG. 8A).
• the second member comprised a cylindrical cavity (referred to as the reservoir) with a diameter of 22 mm and a depth of 20 mils (0.508 mm), giving a volume of approximately 200 ⁇ L
• the members of the fixture were made of metal coated with polytetrafluoroethyle ⁇ e (PTFE),
• the formulation was withdrawn at an initial rate of roughly 15 ⁇ L/min, rising towards a higher rate as the level of formulation reached the center of the mold and then again at a slower rate as the level of formulation continued to fall.
• the formulation moved into the inlet tubing.
• the pump was stopped, the fixture was opened, and the mold removed and placed in a Petri dish.
• the mold was examined for uniformity of fill and specks of microprojection precursor around the periphery. After drying the mold in an incubator at 32°C for 30 minutes, the Petri dish cover was closed, the dish was placed in a foil pouch and heat sealed with nitrogen fill, and was then stored in a refrigerator at 4 0 C.
• a further layer (25% ⁇ o!y(!actic-co-g!ycoi!c acid) in acetonitrile) was cast over the formulation in the mold cavities and dried overnight.
• the resulting array was demolded using a PET strip with 1513 double coated adhesive.
• the array was notch cut with diameter 11 mm, labeled, and stored in a dry chamber.
• Active content and purity were determined using HPLC. The standard deviation of active content in the mold cavities was - 8%.
• a mold for a microprojection array 18 mm by 30 mm, was obtained, A precursor comprising of 14% Dextran 70, 4,8% sorbitol, 2.1% human parathyroid hormone (1 - 34) (hPTH) in histidine buffer solvent, pH 5.5, was prepared. The precursor formulation was sterile filtered through a 0.22 ⁇ m filter. [0117] Fixtures comprised of first and second members was provided (FiG. 6A).
• the second member in one fixture, the second member comprised a cylindrical cavity (or reservoir) with diameter 22 mm and depth 53 mils (1.35 mm, referred to herein as a "one-up reservoir"), In a second fixture, the second member comprised a rectanguiar reservoir with a length of 28 mm and a width of 18 mm referred to herein as a "two-up reservoir").
• the fixture with the two-up reservoir can be oriented either vertically or horizontally in use.
• a valve was employed to close off the venting inlet tube.
• the pressure in the reservoir was then gradually increased to 50 psi (344.7 kPa), as described in Example 5.
• the precursor formulation was withdrawn from reservoir at a certain speed, A desirable amount of precursor formulation was retained in the cavities of the mold(s) after completion of withdrawing of precursor formulation from the reservoir.
• the precursor formulation in cavities of mold was dried at 32 °C for 30 min. Then a basement layer was coated on atop of dried precursor formulation as described in the examples above, to form microstructure array (die cut into 1 cm 2 in diameter), [0121]
• the array was dissolved in buffer and hPTH content was measured by HPLC. As shown in the table below, the amount of precursor formulation retained in the microprojection cavities per cm " array was affected by several factors including, but not limited to, reservoir orientation, depth, precursor withdrawing rate, etc.

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